The present invention relates to the field of electronics packaging and, more particularly, relates to structures for making connections between a semiconductor device carrier and the next level of packaging or between the semiconductor device carrier and the semiconductor device.
In the microelectronics environment, there is a need for high density, high strength packaging to provide interconnection between semiconductor devices and connection from the devices to the electrical power supply. The electrical properties which are desirable include a highly conductive medium in a highly insulative carrier medium having a low dielectric constant.
As to the top surface of the package which contains pads for bonding to a semiconductor device or engineering change pad, the metallization is chosen so as to be best for the pads and the underlying wiring features. This can lead to increased electrical resistance, for instance. Since the pads and the underlying wiring features may have different metallization needs, there is no metallization that ideally suits both needs. The resultant metallization is often a compromise.
Thermally, the package must withstand not only the operating environment but also the thermal excursions encountered during the processing and fabrication of the part. Mechanically, it is preferable to have a substrate package which can withstand chip and pin joining stresses related to interconnecting with the next level of packaging. Moreover, future packages will include pad-on-pad connections along with pin connections on the same substrate for interconnecting with the next level of packaging. The functions of each type of connection may be segregated so that, for example, the pins may be utilized for supplying power while the pads may supply the signals.
Boss, et al. U.S. Pat. No. 4,880,684 disclose an interconnection structure consisting of a capture pad, a polymeric stress relief layer, and a bonding pad for attaching a pin. This reference does not consider the enhanced mechanical requirements for pad-on-pad connections.
Pad-on-pad connections have tougher mechanical requirements so the interconnection structure needs to be stronger to accommodate this type of joining. Too, the metallization on the bottom of the substrate needs to be designed so that the metallization for pad-on-pad and pin joining is manufactured at the same time. The resulting interconnect structure must also be resistant to corrosion.
Accordingly, it is a purpose of the present invention to have an interconnect structure wherein the metallization for the chip attach pads, engineering change pads, and the underlying wiring features can be chosen to ideally provide for the needs of each of these pads and features.
It is another purpose of the present invention to have an interconnect structure that utilizes both pin and pad-on-pad connections.
It is another purpose of the present invention to have an interconnect structure where the substrate metallization structure has been strengthened so as to handle the tougher mechanical requirements of pad-on-pad connections.
It is another purpose of the present invention to have an interconnect structure which has been designed so that the metallization for the pin and pad-on-pad connections can be made at the same time.
It is yet another purpose of the present invention to have an interconnect structure which has been designed so as to meet stringent mechanical requirements while also being resistant to corrosion.
These and other purposes of the present invention will become more apparent after referring to the following description in conjunction with the accompanying drawings.